The present invention relates to lightweight of a battery and a battery having shielding effect and high reliability without sealing leakage.
There is a growing demand for downsizing and lightening of portable electric appliances and the achievement greatly depends upon improvement of battery performance. There have been development and improvement of various batteries in order to meet the demand. Performance required to a battery includes high voltage, high energy density, safety, variety of shape and the like. As a battery used for portable electric appliances, there are a nickel-cadmium (NiCd) battery, a nickel-hydrogen battery (NiMH) and a lithium ion battery until now. In these batteries, a bundle of a positive electrode, a separator and a negative electrode, which is referred to as a battery body, a battery core or a battery element, is stored in a battery case. A can made of metal such as iron, stainless steel or aluminum has been used for the battery case.
Recently, in case of a battery developed for targeting lightweight, for example, a battery using a unified battery body (a battery element) prepared by jointing a positive electrode, a separator and a negative electrode as disclosed in Japanese Unexamined Patent Publication No. 172606/1998, as the battery case material there is used so-called laminated sheet, which is light weight material and is obtained by laminating a polyethylene film or the like to both surfaces of aluminum foil in order to improve weight energy density.
Usually, when a metal can is used as the battery case, either of the positive electrode or the negative electrode is electrically connected to the battery can. The connection is easy in case of using a metal can. For example, if a metal can of iron or stainless is used for the case of a lithium ion battery, the metal can is electrically connected to the negative electrode, while it is electrically connected to the positive electrode when aluminum is used for the metal can. The reason why the connected electrode is changed depending on the material of the battery can is to prevent the battery from corrosion. Thus, in case of conventional batteries using a metal can, the electric potential of the can is consistent with the electric potential of the positive electrode or the negative electrode. As a result, it expressed an effect of electrically (electromagnetically, electrostatically) shielding the battery element and the electric circuit which provides the battery with electric energy.
However, in case of conventional batteries having a laminated sheet material as a battery case, since the metal foil in the laminated sheet does not contact to either the positive electrode or the negative electrode, electric potential is unstable, and there was a problem that it was impossible to obtain electric shielding effect.
The object of the present invention is to provide a means for surely and easily improving shielding effect of a battery using a laminated sheet material for the battery case.
The first battery of the present invention comprises;
a battery body having a positive electrode, a negative electrode and an electrolytic layer interposed between the positive electrode and the negative electrode; a positive electrode lead electrically connected to the positive electrode; a negative electrode lead electrically connected to the negative electrode; a battery case comprising a laminated sheet obtained by laminating a polymer resin and a metal foil, wherein the battery body is stored and the positive electrode lead and the negative electrode lead are sealed to form a hermetic construction; and a means for electrically connecting the metal foil of the battery case to the positive electrode lead or the negative electrode lead. According to this, it is possible to easily and surely maintain the electric potential of the battery case to the electric potential of the positive electrode or the negative electrode, and to electrically (electromagnetically, electrostatically) shield the battery body and the electric circuit to which the battery is connected.
The second battery of the present invention comprises; a battery body having a positive electrode, a negative electrode and an electrolytic layer interposed between the positive electrode and the negative electrode; a positive electrode lead electrically connected to the positive electrode; a negative electrode lead connected to the negative electrode; an outer lead equipped separately from the positive electrode lead and the negative electrode lead; a battery case comprising a laminated sheet obtained by laminating a polymer resin and a metal foil, wherein the battery body is stored and the positive electrode lead, the negative electrode lead and the outer lead are sealed to form a hermetic construction; and a means for electrically connecting the metal foil of the battery case to the outer lead. According to this, it is possible to maintain the electric potential of the battery body to a desired electric potential by an easy and surely means (by inducing the desired electric potential from outside to the outer lead) and to electrically (electromagnetically, statically) shield the battery body and the electric circuit to which the battery is connected.
The third battery of the present invention is that in the first or second battery, the connecting means has a through hole which pierces through the laminated sheet forming the battery case and the lead, wherein the metal foil of the battery case is electrically connected to the positive electrode lead and the negative electrode lead through a conductive material in contact with the wall surface of the through hole. According to this, electrical shielding can be achieved very easily and surely without any extra space.
The fourth battery of the present invention is that in the first or second battery, the connecting means is set on an extended part, which is extended from the sealing part of the laminated sheet forming the battery case. According to this, sealing effect can be surely maintained even when there is not sufficient space for the sealing part.
The fifth battery of the present invention is that in the first or second battery, the connecting means is a means that an exposing part is formed by exposing a part of the outer surface of the metal foil in the laminated sheet forming the battery case, and the exposing part and the lead are electrically connected. According to this, electrical shielding can be achieved very easily and securely without any extra space.
The first process for examining the battery of the present invention is to compare a voltage between an exposing part and a lead with a voltage between a positive electrode lead and a negative electrode lead, wherein the exposing part is formed by exposing a part of the outer surface of the metal foil in the laminated sheet forming the battery case.
The second process for examining the battery of the present invention is that in the first process, a method for exposing a part of the outer surface of the metal foil is to burn out a polymer resin by means of a laser beam.
The third process for examining the battery of the present invention is that in the first process, a method for exposing the part of the outer surface of the metal foil is to expose the part by pressing a needle probe thereto. According to these first to third processes, it is possible to easily and surely examine properties of electrical shield.